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Proof That DNA Is the Genetic Code.

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Proof That DNA Is the Genetic Code. Modern genetics really began with the through and painstaking work of a single scientist Gregor Johann Mendel (1822 - 84). He was imaginative and careful worker who planned his experiments on a large scale. He appreciated that by taking a large number of separate measurements he would eliminate mere chances of effects. He chose to use the garden pea plant (Pisum sativum) for his experiments as it showed several sharply contrasting and easily recognisable characteristics that were without intermediate form, and were relatively unaffected by environment factors. When the inheritance of two pairs of contrasting characteristics was studied he found that each of a pair of contrasting characteristics maybe combined with either of another, that is, the factors show independent assortment. ...read more.


This cell is called a diploid cell. 2. All of the cells of an organism, excluding sperm cells, egg cells, and red blood cells, and all organisms of the same species, were observed to have the same number of chromosomes. 3. The number of chromosomes in any cell appeared to double just before the cell divides by mitosis, in which a single cell splits to form two identical offspring cells. 4. The sex cells (i.e., sperm and egg) appeared to have exactly half of the number of chromosomes as were found in the somatic cells of any organism. The sex cells were shown to have just one copy of each chromosome type. Such cells are called haploid cells. 5. The fertilization of an egg with a sperm cell produces a diploid cell called a zygote, which has the same number of chromosomes as the somatic cells of that organism. ...read more.


These four nitrogenous bases fall into two categories. The purines are double-ringed stuctures that include adenine (A) and guanine (G) and the single-ringed pyrimidines, that include thymine (T) and cytosine (C). Although Miescher and others suspected that the DNA component of nuclein was important for inheritance, others argued that the lack of chemical diversity in DNA ruled out such a possibility. Since DNA only contains four different subunits (A, C, G, and T), it was hard to imagine that this molecule could store the incredible amounts of information necessary to be an effective genetic material. Proteins, on the other hand, consist of chains of twenty different amino acids and could, therefore, be more information-rich. In 1952, American biologists Alfed Hershey and Martha Chase set out to prove that it was DNA that contained the genetic material and proteins. To find this out they used a bacteriophage, a virus which causes disease in bacteria. ...read more.

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